A wireless local area network (WLAN) may be formed by one or more access points (APs) that provide a shared wireless communication medium for use by a number of client devices or stations (STAs). Each AP, which may correspond to a Basic Service Set (BSS), periodically broadcasts beacon frames to enable any STAs within wireless range of the AP to establish and/or maintain a communication link with the WLAN. The beacon frames, which may include traffic indication maps (TIM) and timing synchronization function (TSF) values, are typically broadcast according to a target beacon transmission time (TBTT) schedule. Thus, the beacon frame broadcasts may be separated by a time interval known as the “beacon interval.” In a typical WLAN, only one STA may use the wireless medium at any given time, and each STA may be associated with only one AP at a time.
A STA may locate nearby APs and select a suitable AP with which to associate by performing scanning operations. For example, in passive scanning, the STA listens on one or more wireless channels for beacon frames periodically broadcast by nearby APs. Each beacon frame includes the AP's SSID, supported data rates, synchronization information, and other information related to authenticating and associating with the AP. In active scanning, the STA tries to locate nearby APs, and initiates the scanning process by broadcasting probe request frames. APs within wireless range of the STA response with probe responses that may include information related to authenticating and associating with the AP. Thus, active scanning allows the STA to receive immediate responses from APs (e.g., without waiting for transmission of beacon frames).
Scanning operations may consume significant power. Because many STAs are battery powered, there is a need to reduce the power consumption related to scanning operations. More specifically, there is a need to reduce power consumption of devices that are to be discoverable by other devices during scanning operations.